Download Advanced Operating Systems (CS 202) OS Evolution

Advanced Operating Systems
(CS 202)
OS Evolution and Organization
Jan, 13, 2016
Expectations and little bit
about me
•  I am NOT an OS person
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I drew the short straw J
• 
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My favorite two answers are • 
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My second time teaching this class
I don’t know
What do YOU think?
I am looking forward to learn with you
•  …but I do know a lot about OS
– 
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I am a systems person
I work in architecture, networking, high performance
computing and security
• 
OS is at the intersection of all systems areas
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Coming up
•  Reading for next week (Extensibility):
–  For
Wednesday, Spin (critique) and
Exokernel
–  Friday, L4
–  Links on class website
•  Programming assignment released
Monday
–  Optional
Lab0 released today
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Today
•  Evolution of Operating Systems (and computers!)
– 
Some slides modified from Silberschatz and Gavin, as
well as Margo Seltzer
•  Operating Systems models
•  Why study history? – 
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Understand why OS’s look like they are
Appreciate how and why different pieces evolved
Explain how external forces also shape OS
Provide context for the rest of the quarter
Its interesting!
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Dawn of computing
program
CPU
printer
•  Pre 1950 : the very first electronic computers
–  valves and relays
–  single program with dedicated function
•  Pre 1960 : stored program valve machines
–  single job at a time; OS is a program loader
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Phase 0 of OS Evolution (40s to 1955)
•  No OS
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Computers are exotic, expensive, large, slow
experimental equipment
Program in machine language and using
plugboards
User sits at console: no overlap between
computation, I/O, user thinking, etc..
• 
• 
Program manually by plugging wires in
Goal: number crunching for missile computations
•  Imagine programming that way
– 
Painful and slow
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OS progress in this period
•  Libraries of routines that are common
–  Including
those to talk to I/O devices
–  Punch cards (enabling copying/exchange
of these libraries) a big advance!
–  Pre-cursor to OS
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Phase 1: 1955-1970
•  Computers expensive; people cheap
–  Use
computers efficiently – move people
away from machine
–  OS becomes a batch monitor
• 
• 
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Loads a job, runs it, then moves on to next
If a program fails, OS records memory
contents somewhere
More efficient use of hardware but
increasingly difficult to debug
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•  Batch systems on mainframe computers
– 
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collections of jobs made up into a batch
example: IBM 1401/7094
• 
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card decks spooled onto magnetic tape and from tape to printer
example: English Electric Leo KDF9 32K 48-bit words, 2µsec cycle time
•  punched paper-tape input ‘walk-up’ service or spooling via mag tape
• 
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Advances in technology in this
stage
•  Data channels and interrupts
–  Allow
overlap of I/O and computing
–  Buffering and interrupt handling done by
OS
–  Spool (buffer) jobs onto “high speed”
drums
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Phase 1, problems
•  Utilization is low (one job at a time)
•  No protection between jobs
•  Short jobs wait behind long jobs
–  So,
we can only run one job at a time
•  Coordinating concurrent activities
•  Still painful and slow (but less so?)
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Advances in OS in this period
•  Hardware provided memory support
(protection and relocation)
•  Multiprogramming (not to be confused with
time sharing)
•  Scheduling: let short jobs run first
•  OS must manage interactions between
concurrent things
– 
Starts emerging as a field/science
•  OS/360 from IBM first OS designed to run
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on a family of machines from small to large
Some important projects
•  Atlas computer/OS from Manchester U. (late
50s/early 60s)
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First recognizable OS
Separate address space for kernel
Early virtual memory
•  THE Multiprogramming system (early 60s)
– 
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Introduced semaphores
Attempt at proving systems correct; interesting
software engineering insights
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Not all is smooth
•  Operating systems didn’t really work
•  No software development or structuring tools;
written in assembly
•  OS/360 introduced in 1963 but did not really
work until 1968
– 
Reported on in mythical man month
•  Extremely complicated systems
– 
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5-7 years development time typical
Written in assembly, with no structured programming
Birth of software engineering?
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Phase 2: 1970s
•  Computers and people are expensive
–  Help
people be more productive
–  Interactive time sharing: let many people
use the same machine at the same time
–  Emergence of minicomputers
• 
Terminals are cheap
–  Keep
data online on fancy file systems
–  Attempt to provide reasonable response
times (Avoid thrashing)
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Important advances and
systems
•  Compatible Time-Sharing System
(CTSS)
–  MIT
project (demonstrated in 1961)
–  One of the first time sharing systems
–  Corbato won Turing award in 1990
–  Pioneered much of the work in scheduling
–  Motivated MULTICS
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MULTICS
•  Jointly developed by MIT, Bell Labs and GE
•  Envisioned one main computer to support
everyone
– 
People use computing like a utility like electricity –
sound familiar? Ideas get recycled
•  Many many fundamental ideas: protection rings,
hierarchical file systems, devices as files, …
•  Building it was more difficult than expected
•  Technology caught up
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Sabre system
•  System to run airline systems
–  Still
in use!
•  Minicomputer (then) with terminals for
reservation agents
•  Important ideas such as transaction
processing
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Unix appears
•  Ken Thompson, who worked on MULTICS, wanted to
use an old PDP-7 laying around in Bell labs
•  He and Dennis Richie built a system designed by
programmers for programmers
•  Originally in assembly. Rewritten in C
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If you notice for the paper, they are defending this decision
However, this is a new and important advance: portable
operating systems!
•  Shared code with everyone (particularly universities)
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Unix (cont’d)
•  Berkeley added support for virtual
memory for the VAX
•  DARPA selected Unix as its
networking platform in arpanet
•  Unix became commercial
–  …which
eventually lead Linus Torvald to
develop Linux
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Some important ideas in Unix
•  OS written in a high level language
•  OS portable across hardware platforms
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Computing is no longer a pipe stove/vertical
system
•  Pipes
•  Mountable file systems
•  Many more (we’ll talk about unix later)
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Phase 3: 1980s
•  Computers are cheap, people expensive
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Put a computer in each terminal
CP/M from DEC first personal computer OS (for
8080/85) processors
IBM needed software for their PCs, but CP/M was
behind schedule
Approached Bill Gates to see if he can build one
Gates approached Seattle computer products, bought 86DOS and created MS-DOS
Goal: finish quickly and run existing CP/M software
OS becomes subroutine library and command executive
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New technologies in Phase 3
•  Personal workstations
–  The
PERQ
–  Xerox Alto
–  SUN workstation
•  Personal computers
–  Apple
II
–  IBM PC
–  Macintosh
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New technologies (cont’d)
•  Business applications!
–  Word
processors
–  Spreadsheets
–  Databases
•  Marketplace is broken up horizontally
–  Hardware
–  OS
–  Applications
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New advances in OS
•  PC OS was a regression for OS –  Stepped
back to primitive phase 1 style
OS leaving the cool developments that
occurred in phase 2
•  Academia was still active, and some
developments still occurred in
mainframe and workstation space
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Phase 4: Networked systems
1990s to 2010s
•  Machines can talk to each other
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its all about connectivity
•  We want to share data not hardware
•  Networked applications drive everything
– 
Web, email, messaging, social networks, …
•  Protection and multiprogramming less
important for personal machines
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But more important for servers
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Phase 4, continued
•  Market place continued horizontal stratification
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ISPs (service between OS and applications)
Information is a commodity
Advertising a new marketplace
•  New network based architectures
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Client server
Clusters
Grids
Distributed operating systems
Cloud computing (or is that phase 5?)
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New problems
•  Large scale
–  Google
file system, mapreduce, …
•  Concurrency at large scale –  ACID
(Atomicity, Consistency, Isolation and
Durability) in Internet Scale systems
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Very large delays
Partitioning
•  Security and Privacy
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Phase 5
2010s -- ??
•  New generation?
•  Mobile devices that are powerful
•  Sensing: location, motion, …
•  Cyberphysical systems
•  Computing evolving beyond networked
systems
–  But
OS for them looks largely the same
–  Is that a good idea?
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